This is a second year follow-up study of the socio-emotional development of 120 pre-term and full-term infants, originally seen on three occasions during the first six months of life. The specific aims of the second year study are as follows: 1) To document the changes in expressive behavior of infants as they move into the second year of life, and to specify the emotion socialization practices used by mothers to encourage the regulation of emotion in accord with culturally-defined norms; 2) To evaluate the contribution of the moderator variable of infant "difficultness" to the developmental course of emotion socialization; 3) To specify the relationship between maternal regulatory practices and the actual socio-emotional behaviors of their children at different developmental stages. Method: The standard strange situation procedure, modified to include an extended period of floor-play with the mother in the initial episode, will be used to collect data on a) infant expressive behaviors at 18 months, b) maternal responses to infant behaviors, c) facial and vocal responses to approach of stranger and leave-taking and return of mother, and d) attachment. Infant temperament, maternal emotion and personality variables, and dyadic behaviors during the first half year of life, will serve as predictor variables for patterns of behavior evaluated in the second year study. We anticipate that the second year study will make an important contribution to an understanding of the emotional behaviors of toddler-age children, as well as explicate the relationship between maternal emotional traits and socialization practices, and the socio-emotional behaviors of their children.